Pluggable optical module and optical communication system

ABSTRACT

An object is, in a pluggable optical module, to compactly house an optical fiber used for connecting optical components in a housing in which a plurality of optical components are mounted. The pluggable optical module includes: a plurality of optical components, a printed circuit board; one or more optical fibers; and optical fiber housing means. All or a part of the plurality of optical components are mounted on the printed circuit board. One or more optical fibers connect between the plurality of optical components. The optical fiber housing means includes a guide that is disposed on a plate-like member and can wind the one or more optical fibers, and mounted to be stacked with the printed circuit board on which the optical components are mounted and all or a part of optical components other than the optical components mounted on the printed circuit board.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a National Stage Entry of International ApplicationNo. PCT/JP2016/001939, filed Apr. 7, 2016, which claims priority fromJapanese Patent Application No. 2015-120420, filed Jun. 15, 2015. Theentire contents of the above-referenced applications are expresslyincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a pluggable optical module and anoptical communication system.

BACKGROUND ART

An optical communication system is equipped with an optical module usedfor transmission and reception of an optical signal. In such opticalmodule, particularly in digital coherent communication applications, aplurality of components are mounted in a relatively narrow housing.These plural components are connected by optical fibers that are usedfor connecting the components and arranged in the housing (e.g. PatentLiterature 1).

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Application PublicationNo. 2015-55834

SUMMARY OF INVENTION Technical Problem

However, the inventor has found that the above-described pluggableoptical module used for the digital coherent communication includes someproblems described below. In general, in the pluggable optical modulethat includes a transmission/reception function used for the digitalcoherent communication, one or more optical fibers used for connectingoptical components that connect optical modules, input/outputinterfaces, and the like are disposed.

For example, an interface transmitting an optical signal and an opticaloutput function (e.g. an optical output module) are connected by theoptical fiber. Further, for example, an interface receiving an opticalsignal from the outside and an optical reception function (e.g. anoptical reception module) are connected by the optical fiber.Furthermore, for demodulating an optical signal received in the digitalcoherent communication, it is necessary to perform coherent detection bycausing a modulated optical signal to interfere with a local oscillationlight. Therefore, it is necessary to lead the local oscillation light,which is split from a light of a predetermined wavelength output from alight source included in the optical output function, to the opticalreception function. Thus, an optical fiber that connects between theoptical output function and the optical reception function is required.Accordingly, it is necessary to mount a plurality of optical componentsand a plurality of optical fibers that are required for the digitalcoherent communication in a housing of the pluggable optical module usedfor the digital coherent communication.

However, because a miniaturization requirement for the pluggable opticalmodule used for the digital coherent communication is severe, it isdifficult to arrange and fix the optical fibers in narrow gaps betweenthe components in the housing. Because bending of the optical fiber islimited, when the optical fiber is bent beyond the limit, the opticalfiber will be damaged. Further, when an attempt is made to forciblyhouse the optical fiber in the housing, the optical fiber and theoptical component may interfere with each other, the optical fiber maybe damaged, or a breakage of the optical fiber may occur.

The present invention has been made in view of the aforementionedcircumstances and aims to, in a pluggable optical module, compactlyhouse an optical fiber used for connecting optical components in ahousing in which a plurality of optical components are mounted.

Solution to Problem

An aspect of the present invention is a pluggable optical moduleincluding: a plurality of optical components; a printed circuit board onwhich all or a part of the plurality of optical components are mounted;one or more optical fibers connecting between the plurality of opticalcomponents; and optical fiber housing means including a guide that isdisposed on a plate-like member and configured to be capable of windingthe one or more optical fibers, the optical fiber housing means beingmounted to be stacked with the printed circuit board on which theoptical components are mounted and all or a part of optical componentsother than the optical components mounted on the printed circuit board.

An aspect of the present invention is a pluggable optical communicationsystem including: an optical fiber configured to transmit an opticalsignal; a pluggable optical module configured in such a manner that theoptical fiber is insertable into and removable from the pluggableoptical module, the pluggable optical module outputting the opticalsignal to the optical fiber; and an optical communication apparatusconfigured in such a manner that the pluggable optical module isinsertable into and removable from the optical communication apparatus,in which the pluggable optical module includes: a plurality of opticalcomponents; a printed circuit board on which all or a part of theplurality of optical components are mounted; one or more optical fibersconnecting between the plurality of optical components; and opticalfiber housing means including a guide disposed on a plate-like memberand configured to be capable of winding the one or more optical fibers,the optical fiber housing means being mounted to be stacked with theprinted circuit board on which the optical components are mounted andall or a part of the optical components other than the opticalcomponents mounted on the printed circuit board.

Advantageous Effects of Invention

According to the present invention, in a pluggable optical module, it ispossible to compactly house an optical fiber used for connecting opticalcomponents in a housing in which a plurality of optical components aremounted.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a pluggable optical module according toa first exemplary embodiment observed from a side of an optical fiber;

FIG. 2 is a perspective view of the pluggable optical module accordingto the first exemplary embodiment observed from a side of an opticalcommunication apparatus;

FIG. 3A is a perspective view scematically illustrating an example of aninternal configuration of the pluggable optical module 100 according tothe first exemplary embodiment;

FIG. 3B is a perspective view schematically illustrating an example ofthe internal configuration of the pluggable optical module 100 accordingto the first exemplary embodiment;

FIG. 3C is a perspective view schematically illustrating an example ofthe internal configuration of the pluggable optical module 100 accordingto the first exemplary embodiment;

FIG. 4 is a block diagram schematically illustrating a configuration ofthe pluggable optical module according to the first exemplaryembodiment;

FIG. 5 is a block diagram illustrating a configuration example of a mainpart of an optical communication system in which the pluggable opticalmodule according to the first exemplary embodiment is mounted;

FIG. 6 is a block diagram illustrating a configuration example of anoptical output module according to the first exemplary embodiment;

FIG. 7 is a diagram schematically illustrating a configuration of anoptical modulation unit according to the first exemplary embodiment;

FIG. 8 is a perspective view schematically illustrating a configurationof optical fiber housing means according to the first exemplaryembodiment;

FIG. 9 is a top view schematically illustrating a housing example of anoptical fiber in optical fiber housing means according to a secondexemplary embodiment;

FIG. 10 is a top view schematically illustrating another housing exampleof the optical fiber in the optical fiber housing means according to thesecond exemplary embodiment;

FIG. 11 is a top view schematically illustrating another housing exampleof the optical fiber in the optical fiber housing means according to thesecond exemplary embodiment;

FIG. 12 is a diagram illustrating a housing example of the optical fiberwhen the first to third circular paths are combined;

FIG. 13 is a top view schematically illustrating a configuration ofoptical fiber housing means according to a third exemplary embodiment;and

FIG. 14 is a top view schematically illustrating a configuration ofoptical fiber housing means according to a fourth exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the present invention will be described belowwith reference to the drawings. The same components are denoted by thesame reference numerals throughout the drawings, and a repeatedexplanation is omitted as needed.

First Exemplary Embodiment

A pluggable optical module 100 according to a first exemplary embodimentwill be described. The pluggable optical module 100 is configured insuch a manner that a connector part of an optical fiber with connectoris insertable into or removable from the pluggable optical module 100.The pluggable optical module 100 is also configured to be insertableinto or removable from an external optical communication apparatus, forexample.

First, an appearance of the pluggable optical module 100 will bedescribed. FIG. 1 is a perspective view of the pluggable optical module100 according to the first exemplary embodiment observed from a side ofan insertion port of the optical fiber. A numerical sign 61 shown inFIG. 1 indicates an upper surface of the pluggable optical module 100. Anumerical sign 62 shown in FIG. 1 indicates an insertion port of aconnector of the optical fiber with connector. FIG. 2 is a perspectiveview of the pluggable optical module 100 according to the firstexemplary embodiment observed from a side of the optical communicationapparatus. A numerical sign 63 shown in FIG. 2 indicates a lower surfaceof the pluggable optical module 100. A numerical sign 64 shown in FIG. 2indicates a connection part with the optical communication apparatus 93.

Next, a basic internal configuration of the pluggable optical module 100will be described. FIG. 3A is a perspective view schematicallyillustrating an example of the internal configuration of the pluggableoptical module 100 according to the first exemplary embodiment. FIG. 3Ais the perspective view of the pluggable optical module 100 according tothe first exemplary embodiment observed from the side of the opticalcommunication apparatus. Note that FIG. 3A illustrates the example inwhich a lid of the lower surface constituting a housing 10 (thenumerical sign 63 in FIG. 2) is removed.

As illustrated in FIG. 3A, plate-like optical fiber housing means 14 ismounted in an upper surface side (Z+ side) of the housing 10 in such amanner that a surface on which the optical fiber is housed faces upward(Z+ side). Further, a printed circuit board 51, on which optical modules(one or both of an optical output module and an optical receptionmodule), a pluggable electric connector, and the like are mounted, ismounted at a position where the printed circuit board 51 does notinterfere with the optical fiber housing means 14, and a surface of theprinted circuit board 51 on which components are mounted faces upward(Z+ direction). Furthermore, optical modules (one or both of the opticaloutput module and the optical reception module) are mounted below (Z−side) the optical fiber housing means 14, Here, an optical output module12 described below is used as an example of the optical module.

The optical fiber housing means 14 is formed as a plate-like member, andthe optical fibers that connect between optical components mounted inthe pluggable optical module 100 are wound in this plate. Here, anexample of an optical fiber used for connecting optical components, anoptical fiber F1 that connects the optical output module 12 with anotheroptical component mounted on the printed circuit board 51 via theoptical fiber housing means 14 is illustrated. As illustrated in FIG.3A, the optical fiber housing means 14 can be arranged, in the housing,above and below the other components and the printed circuit board onwhich the other components are mounted. In this case, it is desirablethat the optical fiber housing means 14 is disposed in such a mannerthat the surface of the optical fiber housing means 14 on which theoptical fiber is housed does not face the other components and theprinted circuit board 51. In other words, it is desirable that theoptical fiber housing means 14 is disposed in such a manner that thelower surface of the optical fiber housing means 14 faces the othercomponents and the printed circuit board 51. As a result, it is possibleto prevent the optical fiber from being damaged. In this example, asdescribed below, when the optical components including the opticaloutput module 12 and the optical fiber housing means 14 are housed inthe hosing 10, an extra length of the optical fiber (e.g. the opticalfiber F1) is wound by the optical fiber housing means 14. Accordingly,the optical fiber for connecting the optical components in the housing10 is housed in the housing 10 not to interfere with the other opticalcomponents and the printed circuit board 51.

A modified example of the basic internal configuration of the pluggableoptical module 100 will be described. FIG. 3B is a perspective viewschematically illustrating an example of the internal configuration ofthe pluggable optical module 100 according to the first exemplaryembodiment. As in FIG. 3A, FIG. 3B is the perspective view of thepluggable optical module 100 according to the first exemplary embodimentobserved from the side of the optical communication apparatus. As inFIG. 3A, FIG. 3B illustrates the example in which the lid of the lowersurface constituting the housing 10 (the numerical sign 63 in FIG. 2) isremoved.

As illustrated in FIG. 3B, a printed circuit board 52, on which apluggable electric connector and the like are mounted, is mounted in theupper surface side of the housing 10 (Z+ side). The plate-like opticalhousing means 14 is mounted to be stacked with the printed circuit board52 in the Z direction. The surface of the optical housing means 14 onwhich the optical fiber is housed may face upward (Z+ side) or downward(Z− side). The optical housing means 14 is configured as the plate-likemember having a small thickness in the Z direction so that the opticalhousing means 14 can be easily stacked with the printed circuit board52. The other configurations are similar to that in FIG. 3A.

In this example, as described below, when the optical componentsincluding the optical output module 12 and the optical fiber housingmeans 14 are housed in the hosing 10, the extra length of the opticalfiber (e.g. the optical fiber F1) is wound by the optical fiber housingmeans 14. Accordingly, the optical fiber used for connecting the opticalcomponents in the housing 10 is housed in the housing 10 not tointerfere with the other optical components and the printed circuitboard 52.

Another modified basic internal configuration of the pluggable opticalmodule 100 will be described. FIG. 3C is a perspective viewschematically illustrating an example of the internal configuration ofthe pluggable optical module 100 according to the first exemplaryembodiment. As in FIG. 3A, FIG. 3C is the perspective view of thepluggable optical module 100 according to the first exemplary embodimentobserved from the side of the optical communication apparatus. As inFIG. 3A, FIG. 3C illustrates the example in which the lid of the lowersurface constituting the housing 10 (the numerical sign 63 in FIG. 2) isremoved.

As illustrated in FIG. 3C, a printed circuit board 53, on which apluggable electric connector and the like are mounted, is mounted in theupper surface side of the housing 10 (Z+ side). The plate-like opticalhousing means 14 and the optical output module 12 are mounted to bestacked with the printed circuit board 53 in the Z direction. Thesurface of the optical housing means 14 on which the optical fiber ishoused may face upward (Z+ side) or downward (Z− side). A printedcircuit board 54, on which other optical components are mounted, ismounted to be stacked with the printed circuit board 53 and the opticalfiber housing means 14 in the Z direction. Even in this case, theoptical housing means 14 is configured as the plate-like member havingthe small thickness in the Z direction so that the optical housing means14 can be easily stacked with the printed circuit boards 53 and 54(first and second printed circuit boards).

Here, optical fibers F2 and F3 are disposed as the optical fibers usedfor connecting the optical components. For example, the optical fiber F2connects the optical output module 12 and another optical componentmounted on the printed circuit board 53 via the optical fiber housingmeans 14. For example, the optical fiber F3 connects the optical outputmodule 12 and another optical component mounted on the printed circuitboard 54 via the optical fiber housing means 14. In this example, asdescribed below, when the optical components such as the optical outputmodule 12 and the optical fiber housing means 14 are housed in thehosing 10, extra lengths of the optical fibers (e.g. the optical fibersF2 and F3) are wound by the optical fiber housing means 14. Accordingly,the optical fibers used for connecting the optical components in thehousing 10 are housed in the housing 10 not to interfere with the otheroptical components and the printed circuit boards 53 and 54.

FIG. 3A to FIG. 3C are merely examples. Therefore, as long as it ispossible to prevent the optical fiber from being damaged, the surface ofthe optical fiber housing means 14 on which the optical fiber is housedmay face upward (Z+ side) or downward (Z− side). Further, as long as itis possible to prevent the optical fiber from being damaged, the surfaceof the printed circuit board on which the optical components and thelike are mounted may face upward (Z+ side) or downward (Z− side).

As described above, according to the present configuration, it can beunderstood that it is possible to house the optical fiber used foroptical connection in the pluggable optical module 100 not to interferewith the other components.

Next, the basic internal configuration of the pluggable optical module100 will be described in more detail. FIG. 4 is a block diagramillustrating the configuration of the pluggable optical module 100according to the first exemplary embodiment in more detail. FIG. 5 is ablock diagram illustrating a configuration example of a main part of theoptical communication system 1000 in which the pluggable optical module100 according to the first exemplary embodiment is mounted. Asillustrated in FIG. 5, the pluggable optical module 100 is configured insuch a manner that the connectors of the optical fibers with connector91 and 92 are insertable into and removable from the pluggable opticalmodule 100. For example, an LC connector and MU connector can be used asthe connectors of the optical fibers with connector 91 and 92. Thepluggable optical module 100 is controlled based on a control signalCON1 input from the optical communication apparatus 93 that is acommunication host. The pluggable optical module 100 can also receive amodulation signal MOD that is a data signal from the opticalcommunication apparatus 93 with the control signal CON1. In this case,the pluggable optical module 100 may output an optical signal LS1 (alsoreferred to as a first optical signal) modulated based on the receivedmodulation signal MOD through the optical fiber 91. The pluggableoptical module 100 may also output a data signal DAT corresponding to anoptical signal LS2 (also referred to as a second optical signal)received from the outside through the optical fiber 92 to the opticalcommunication apparatus 93. For example, the optical communicationapparatus 93 performs communication signal processing such as flamingprocessing of a communication data signal from the pluggable opticalmodule 100 or a communication data signal input to the pluggable opticalmodule 100.

The pluggable optical module 100 includes a pluggable electric connector11, the optical output module 12, an optical reception module 13, theoptical fiber housing means 14, a pluggable optical receptor 15, a firstoptical fiber F11, a second optical fiber F12, and a third optical fiberF13.

The pluggable electric connector 11 is configured to be insertable intoand removable from the optical communication apparatus 93. The pluggableelectric connector 11 receives the control signal CON1 that is anelectric signal output from the optical communication apparatus 93 andforwards the control signal CON1 to one or both of the optical outputmodule 12 and the optical reception module 13. The pluggable electricconnector 11 receives the modulation signal MOD that is an electricsignal output from the optical communication apparatus 93 and forwardsthe modulation signal MOD to the optical output module 12. The pluggableelectric connector 11 forwards the data signal DAT output from theoptical reception module 13 to the optical communication apparatus 93.

The optical output module 12 is controlled based on the control signalCON1 input from the optical communication apparatus 93 through thepluggable electric connector 11, and outputs an optical signal LS1modulated based on the modulation signal MOD input from the opticalcommunication apparatus 93 through the pluggable electric connector 11.The optical output module 12 includes a light source and a Mach-Zehndertype optical modulator. The Mach-Zehnder type optical modulatormodulates a light from the light source with a predetermined modulationmethod to output the optical signal LS1. The optical output module 12modulates the optical signal LS1 by applying the modulation signal MODto phase modulation areas formed on optical waveguides of theMach-Zehnder type optical modulator. The optical output module 12 canmodulate the optical signal LS1 with various modulation methods such asphase modulation, amplitude modulation and polarization modulation, or acombination of the various modulation methods. Here, for example, theMach-Zehnder type optical modulator is a semiconductor optical modulatoror another optical modulator.

Here, the phase modulation area is an area that includes an electrodeformed on the optical waveguide. An effective refractive index of theoptical waveguide below the electrode is changed by applying an electricsignal, e.g. a voltage signal, to the electrode. As a result, asubstantial optical length of the optical waveguide in the phasemodulation area can be changed. Thus, the phase modulation area canchange a phase of the optical signal propagating through the opticalwaveguide. Then, the optical signal can be modulated by providing aphase difference between the optical signals propagating through twooptical waveguides.

A configuration example of the optical output module 12 will bedescribed. FIG. 6 is a block diagram illustrating the configurationexample of the optical output module 12 according to the first exemplaryembodiment. The optical output module 12 includes a light source 16 andan optical modulation unit 17. The light source 16 is, for example, awavelength-tunable optical module that includes a semiconductor laserdevice and a ring oscillator and outputs an output light Lorig.

The optical modulation unit 17 is the Mach-Zehnder type opticalmodulator, for example. Note that the optical modulation unit 17 outputsthe optical signal LS1 generated by modulating the output light Lorig inresponse to the modulation signal MOD corresponding to the communicationdata signal input from the optical communication apparatus 93 throughthe pluggable electric connector 11. A part of the light output from thelight source 16 (the output light Lorig) is split, for example, by anoptical splitter. The split light is output to the optical receptionmodule 13 through the second optical fiber F12 as a local oscillationlight LO.

Subsequently, a configuration of the optical modulation unit 17 will bedescribed. FIG. 7 is a diagram schematically illustrating theconfiguration of the optical modulation unit 17 according to the firstexemplary embodiment. The optical modulation unit 17 is configured as ageneral Mach-Zehnder type optical modulator. The optical modulation unit17 includes an optical modulator 17A and a driver circuit 17B.

The optical modulator 17A modulates the output light Lorig from thelight source 16 to output the optical signal LS1. The optical modulator17A includes optical waveguides 171 to 174, and phase modulation areasPMA and PMB. The output light Lorig from the light source 16 is input toone end of the optical waveguide 171. The other end of the opticalwaveguide 171 is optically connected with one end of the opticalwaveguide 172 and one end of the optical waveguide 173. Thus, a lightpropagating through the optical waveguide 171 is branched toward theoptical waveguide 172 and the optical waveguide 173. The other end ofthe optical waveguide 172 and the other end of the optical waveguide 173are connected with one end of the optical waveguide 174. On the opticalwaveguide 172, the phase modulation area PMA that changes a phase of alight propagating through the optical waveguide 172 is disposed. On theoptical waveguide 173, the phase modulation area PMB that changes aphase of a light propagating through the optical waveguide 173 isdisposed. The light signal LS1 is output from the other end of theoptical waveguide 174.

The driver circuit 17B can control a modulation operation of the opticalmodulator 17A. The driver circuit 17B can also control a bias point ofthe optical modulator 17A by applying a bias voltage VBIAS to one orboth of the phase modulation areas PMA and PMB in response to thecontrol signal CON1. Hereinafter, it is assumed that the driver circuit17B applies the bias voltage to the phase modulation areas PMA and PMB.The driver circuit 17B can also modulate the optical signal LS1 byapplying the modulation signal MOD to one or both of the phasemodulation areas PMA and PMB. In this example, the driver circuit 17Bapplies a modulation signal SIG_M1 to the phase modulation area PMA inresponse to the modulation signal MOD. The driver circuit 17B applies amodulation signal SIG_M2 to the phase modulation area PMB in response tothe modulation signal MOD.

Although not illustrated, the optical output module 12 may include anoptical adjustment unit. The optical adjustment unit may adjust power ofthe optical signal LS1 by attenuating or blocking the optical signal LS1output from the optical output module 12. The optical adjustment unitmay adjust the power of the optical signal LS1 in response to thecontrol signal CON1 or a control signal other than the control signalCON1 input from the optical communication apparatus 93 through thepluggable electric connector 11. For example, an optical attenuator maybe used as the optical adjustment unit.

The optical reception module 13 demodulates the optical signal LS2received from the outside through the optical fiber 92 by causing theoptical signal LS2 to interfere with the local oscillation light LO fromthe light source 16 of the optical output module 12. The opticalreception module 13 outputs the data signal DAT that is a demodulatedelectric signal to the optical communication apparatus 93 through thepluggable electric connector 11.

The optical fiber housing means 14 has a configuration for winding andhousing the extra lengths of the first to third optical fibers F11 toF13 disposed in the pluggable optical module 100. The optical fiberhousing means 14 can be configured, for example, using resin. Theoptical fiber housing means 14 can be easily manufactured, for example,by injection forming using a mold. In this example, the optical fiberhousing means 14 includes circular guides G11 to G13 (also referred toas first to third guides) configured to respectively wind the first tothird optical fibers F11 to F13. FIG. 8 is a perspective viewschematically illustrating a configuration of the optical fiber housingmeans 14 according to the first exemplary embodiment. In this example,as illustrated in FIG. 8, the circular guides G11 to G13 will bedescribed as a thin cylindrical (or disk-like) member whose axialdirections is a direction perpendicular to the planes of FIGS. 4 and 5(i.e. Z direction) and as formed on a plate 14A, for example, made ofresin.

The first optical fiber F11, the second optical fiber F12, and the thirdoptical fiber F13 are the optical fibers for connecting the opticalcomponents that connect a plurality of the optical components (e.g. theoptical output module 12, the optical reception module 13, and thepluggable optical receptor 15) in the pluggable optical module 100. Oneend of the first optical fiber F11 is connected with the optical outputmodule 12 and the other end of the first optical fiber F11 is connectedwith the pluggable optical receptor 15. The optical signal LS1 outputfrom the optical output module 12 propagates through the first opticalfiber F11 and enters into the pluggable optical receptor 15. The extralength between both ends of the first optical fiber F11 is housed insuch a manner that the first optical fiber F11 is wound around an outerperimeter of the circular guide G11 one or more times. Thus, the firstoptical fiber F11 longer than a distance between the optical outputmodule 12 and the pluggable optical receptor 15 can be effectivelyhoused and it is possible to prevent the first optical fiber F11 fromtangling and interfering with the other optical components in thepluggable optical module 100. Note that the circular guide G11 isconfigured in such a manner that a bending curvature CV1 of the firstoptical fiber F11 due to winding does not exceed a maximum allowablebending curvature MCV1 of the first optical fiber F11 (i.e. CV1<MCV1).For example, a curvature GCV1 of an outer perimeter surface of thecircular guide G11 is designed not to exceed the maximum allowablebending curvature MCV1 of the first optical fiber F11 (i.e. GCV1<MCV1).

One end of the second optical fiber F12 is connected with the opticaloutput module 12 and the other end of second optical fiber F12 isconnected with the optical reception module 13. The local oscillationlight LO output from the optical output module 12 propagates through thesecond optical fiber F12 and enters into the optical reception module13. The extra length between both ends of the second optical fiber F12is housed in such a manner that the second optical fiber F12 is woundaround an outer perimeter of the circular guide G12, for example, one ormore times. Thus, the second optical fiber F12 longer than a distancebetween the optical output module 12 and the optical reception module 13can be effectively housed and it is possible to prevent the secondoptical fiber F12 from tangling and interfering with the other opticalcomponents in the pluggable optical module 100. Note that the circularguide G12 is configured in such a manner that a bending curvature CV2 ofthe second optical fiber F12 due to winding does not exceed a maximumallowable bending curvature MCV2 of the second optical fiber F12 (i.e.CV2<MCV2). For example, a curvature GCV2 of an outer perimeter surfaceof the circular guide G12 is designed not to exceed the maximumallowable bending curvature MCV2 of the second optical fiber F12 (i.e.GCV2<MCV2).

One end of the first optical fiber F13 is connected with the opticalreception module 13 and the other end of the first optical fiber F13 isconnected with the pluggable optical receptor 15. The optical signal LS2from the pluggable optical receptor 15 propagates through the thirdoptical fiber F13 and enters into the optical reception module 13. Theextra length between both ends of the third optical fiber F13 is housedin such a manner that the third optical fiber F13 is wound around anouter perimeter of the circular guide G13 one or more times. Thus, thethird optical fiber F13 longer than a distance between the opticalreception module 13 and the pluggable optical receptor 15 can beeffectively housed and it is possible to prevent the third optical fiberF13 from tangling and interfering with other optical components in thepluggable optical module 100. Note that the circular guide G13 isconfigured in such a manner that a bending curvature CV3 of the thirdoptical fiber F13 due to winding does not exceed a maximum allowablebending curvature MCV3 of the third optical fiber F13 (i.e. CV3<MCV3).For example, a curvature GCV3 of the outer perimeter surface of thecircular guide G13 is designed not to exceed the maximum allowablebending curvature MCV3 of the third optical fiber F13 (i.e. GCV3<MCV3).

In the above-described example, each of the circular guides G11 to G13is described as an independent member, and, however, it is merely anexample. For example, one circular guide may wind and house a pluralityof the optical fibers, in sum, two circular guides may be disposed, onecircular guide may wind and house two optical fibers (e.g. the firstoptical fiber F11 and the second optical fiber F12) and the othercircular guide may wind and house one optical fiber (e.g. the thirdoptical fiber F13). Further, one circular guide may be disposed, the onecircular guide may wind and house all optical fibers (e.g. the firstoptical fiber F11, the second optical fiber F12, and the third opticalfiber F13).

In the above-described example, each of the circular guides G11 to G13is described, and, however, the shape of the guide is not limited to thecircular shape. As long as the bending curvature of the optical fibercircling the outer perimeter does not exceed the maximum allowablebending curvature of the optical fiber, the guide may be of any shapesuch as an ellipse, a rounded square, a rounded rectangle, and anarbitrary polygon (whose corner may be formed by a curved line or astraight line). Further, the optical fiber circling the guide may circlein contact with the outer perimeter of the guide or may circle along aroute separated from the outer perimeter of the guide. Furthermore,although it is described above that the optical fiber circles the outerperimeter of the guide, this does not represent the optical fiber needsto make one revolution around the outer perimeter of the guide. Ahousing mode in which the optical fiber is bent along the outerperimeter of the guide in a route shorter than the one revolution suchas ½ or ¼ of the outer perimeter is included. This is the same not onlyin the present exemplary embodiment, but also in the following exemplaryembodiments.

The pluggable optical receptor 15 is configured in such a manner thatthe connectors of the external optical fibers 91 and 92 are insertableinto and removable from the pluggable optical receptor 15.

In general, in a pluggable optical module used for the digital coherentoptical communication, not only is it necessary to mount a plurality ofcomponents (the pluggable electric connector 11, the optical outputmodule 12, the optical reception module 13, the optical fiber housingmeans 14, and the pluggable optical receptor 15 in the present exemplaryembodiment) in the module, but also miniaturization of the size of thepluggable optical module is strongly required. Therefore, it isnecessary to house a plurality of components in a relatively narrowhousing and connect between the components using an optical fiber asnecessary. However, it is difficult to prepare an optical fiber havingan optimum length for each application due to variations in mountingpositions of components and variations in cutting lengths of the opticalfiber. Even when it can be achieved, the number of steps will increase.However, according to the present configuration, by preparing an opticalfiber having a margin for a required length and winding the opticalfiber around the optical guide as appropriate, the components in thepluggable optical module can be connected while compactly housing anextra part of the optical fiber. Therefore, without being affected byvariations in mounting of parts and variations in cutting of fibers, itis possible to easily achieve an optical connection in the pluggableoptical module using the optical fiber.

Further, in the present configuration, since the optical fiber used inthe pluggable optical module has the margin length, it is possible toprevent an unnecessary tension from applying to the optical fiber whenarranging the optical fiber between the different components via theguide. As a result, it is possible to prevent the optical fiber frombeing damaged in a manufacturing process of the pluggable opticalmodule, and it can be understood that it is advantageous from theviewpoint of improving a manufacturing yield.

Furthermore, according to the present configuration, since a housingpart of the optical fiber does not interfere with the other componentsand does not shift from the housed position, it is possible to prevent asituation that the housed optical fiber is damaged by contacting theother components. Thus, the optical fiber is not damaged even when theoptical fiber receives a vibration and shock when the pluggable opticalmodule is inserted into another apparatus. Therefore, it can beunderstood that the present configuration is advantageous from theviewpoint of preventing malfunction of the pluggable optical module 100in operation.

Further, according to the present configuration, since the optical fibercan be housed in the plate-like optical fiber housing means in acircular pattern, a thickness in the optical fiber housing means can besuppressed. Therefore, the optical fiber housing means can be mounted ina narrow gap in the housing. Hence, it can be understood that it isadvantageous from a view point of miniaturization of the pluggableoptical module.

Second Exemplary Embodiment

A pluggable optical module 200 according to a second exemplaryembodiment will be described. The pluggable optical module 200 accordingto the second exemplary embodiment has a configuration in which theoptical fiber housing means 14 of the pluggable optical module 100according to the first exemplary embodiment is replaced with opticalfiber housing means 24. In the present exemplary embodiment, the opticalfiber housing means 24 includes at least two guides to house and wind anoptical fiber.

FIG. 9 is a top view schematically illustrating a housing example of theoptical fiber in the optical fiber housing means 24 according to thesecond exemplary embodiment. The optical fiber housing means 24 has aconfiguration for housing and winding the first to third optical fibersF11 to F13 disposed in the pluggable optical module 100. The opticalfiber housing means 24 can be configured, for example, using resin. Theoptical fiber housing means 24 can be easily manufactured, for example,by injection forming using a mold. In this example, the optical fiberhousing means 24 includes circular guides G21 and G22 disposed on aplate 24A and configured to respectively wind the first to third opticalfibers F11 to F13. In this example, in the same way as the circularguides G11 to G13 in FIG. 4, the circular guides G21 and G22 will bedescribed as a thin cylindrical (or disk-like) member whose axisdirection is a direction perpendicular to the plane of FIG. 9. In theoptical fiber housing means 24 of FIG. 9, the first optical fiber F11circles around one circular guide (the circular guide G11) and therebythe optical filer is housed (Hereinafter, it is referred to as a firstcircular path.).

FIG. 10 is a top view schematically illustrating another housing exampleof the optical fiber in the optical fiber housing means 24 according tothe second exemplary embodiment. In this example, each optical fibercircles around a plurality of circular guides. Specifically, the firstoptical fiber F11 is housed by circling around outer perimeters of thecircular guides G21 and G22 of the optical fiber housing means 24, forexample. As illustrated in FIG. 10, the first optical fiber F11 can behoused by circling around the circular guides G21 and G22 once tosurround the circular guides G21 and G22 (Hereinafter, it is referred toas a second circular path.).

FIG. 11 is a top view schematically illustrating another housing exampleof the optical fiber in the optical fiber housing means 24 according tothe second exemplary embodiment. In this example, by causing the opticalfiber to cross between the circular guides G21 and G22, and by causingthe first optical fiber F11 to circle in such a manner that circlingdirections around the circular guides G21 and the circular guides G22are different from each other, the first optical fiber F11 can be alsohoused (Hereinafter, it is referred to as a third circular path.).

Further, the above-described first to third circular paths can becombined as appropriate. FIG. 12 is a diagram illustrating a housingexample of the optical fiber when the first to third circular paths arecombined. Note that, in the above examples, it should be appreciatedthat the first optical fiber F11 can be derived to any direction at anyposition on the circular path.

As described above in the present exemplary embodiment, one or moreoptical fibers can be wound by any of a plurality of types of pathsbetween a plurality of guides or by a combination of a plurality oftypes of paths. Thus, the length of the optical fiber to be wound can beadjusted in multiple stages, and thereby it is possible to correspond tohousing of various length optical fibers.

Note that, although the first optical fiber F11 has been illustrated inFIGS. 9 to 12, it should be appreciated that the second optical fiberF12 and the third optical fiber F13 can be housed in the same manner.

Third Exemplary Embodiment

A pluggable optical module 300 according to a third exemplary embodimentwill be described. The pluggable optical module 300 has a configurationin which the optical fiber housing means 24 of the pluggable opticalmodule 200 according to the second exemplary embodiment is replaced withoptical fiber housing means 34. Hereinafter, the optical fiber housingmeans 34 will be described.

FIG. 13 is a top view schematically illustrating a configuration of theoptical fiber housing means 34 according to the third exemplaryembodiment. The optical fiber housing means 34 has a configuration inwhich a splice housing 30 is added to the optical fiber housing means24. In the present exemplary embodiment, a splice 31 that is a part inwhich two optical fibers are spliced (e.g. by fiber fusion) is disposedin the first optical fiber F11. The splice 31 is fixed by being housedin the splice housing 30 disposed on the plate 24A of the optical fiberhousing means 34.

In general, the splice 31 is reinforced by covering a spliced part oftwo optical fibers with a reinforcing sleeve. For example, a groove intowhich the sleeve of the splice 31 is embedded is disposed in the splicehousing 30. By embedding the splice 31 into this groove, the splice 31can be fixed.

In general, in the optical fiber including the splice, a mechanicalstrength against pulling and bending of the spliced part of the fiber inthe splice becomes smaller as compared with other parts. Thus, in thepresent configuration, by fixing the splice 31 with the splice housing30, it is possible to suppress a movement of the splice 31 when a forceis applied to the optical fiber and to reduce a burden on the splicedpart of the optical fiber. As a result, even when the force is appliedto the optical fiber when the optical fiber is arranged and the opticalfiber housing means is attached, it is possible to prevent a breakage ofthe optical fiber from occurring.

Note that, although the first optical fiber F11 has been illustrated inFIG. 13, it should be appreciated that the second optical fiber F12 andthe third optical fiber F13 can be housed in the same manner.

Fourth Exemplary Embodiment

A pluggable optical module 400 according to a fourth exemplaryembodiment will be described. The pluggable optical module 400 has aconfiguration in which the optical fiber housing means 14 of thepluggable optical module 100 according to the first exemplary embodimentis replaced with optical fiber housing means 44. Hereinafter, theoptical fiber housing means 44 will be described.

FIG. 14 is a top view schematically illustrating a configuration of theoptical fiber housing means 44 according to the fourth exemplaryembodiment. The optical fiber housing means 44 includes circular guidesG31 and G32, and guides G33 and G34 (also referred to as fourth toseventh guides). The circular guides G31 and G32 are disposed atdiagonal positions of a square, respectively. The guides G33 and G34 aredisposed at the diagonal positions of the square other than thepositions at which the circular guides G31 and G32 are disposed,respectively.

Note that, for simplicity of the drawing, the optical fiber is denotedby a sign F in FIG. 14. In sum, the optical fiber F represents any ofthe first to third optical fibers F11 to F13. A coarse hatching partrepresents an upper surface of the guide and a surface having the sameheight as the upper surface of the guide. A dense hatching partrepresents a bottom surface of a groove through which the optical fiberpasses. The bottom surface of the groove is lower than the upper surfaceof the guide.

The circular guides G31 and G32 can each wind the optical fiber usingthe first to third paths as in the second exemplary embodiment. Theoptical fiber can be bent along curved parts of the guides G33 and G34.

As illustrated in FIG. 14, the optical fiber can pass through a paththat is from an outer perimeter of the circular guide G31 to an outerperimeter of the circular guide G32 via the curved part of the guide G33(Needless to say that the optical fiber can pass through this path in anopposite direction.). The optical fiber can pass through a path that isfrom the outer perimeter of the circular guide G31 to the outerperimeter of the circular guide G32 via the curved part of the guide G34(Needless to say that the optical fiber can pass through this path in anopposite direction.).

The optical fiber can be also arranged between the circular guide G31and the guide G33 to the circular guides G31 and G32, and the guide G34(Needless to say that the optical fiber can pass through this path in anopposite direction.). The optical fiber can be also arranged between thecircular guide G32 and the guide G33 to the circular guides G31 and G32,and the guide G34 (Needless to say that the optical fiber can passthrough this path in an opposite direction.). The optical fiber can bealso arranged between the circular guide G31 and the guide G34 to thecircular guides G31 and G32, and the guide G33 (Needless to say that theoptical fiber can pass through this path in an opposite direction.). Theoptical fiber can be also arranged between the circular guide G32 andthe guide G33 to the circular guides G31 and G32, and the guide G33(Needless to say that the optical fiber can pass through this path in anopposite direction.).

The optical fiber housing means 44 includes projections 41 that projectoutward from outer perimeter surfaces of the circular guides G31 andG32, and the guides G33 and G34. The projects 41 projecting inward arealso disposed inside an outer frame 40 that is formed to surround thecircular guides G31 and G32, and the guides G33 and G34. The projection41 is configured in such a manner that the optical fiber can passthrough the lower side of the projection 41. Thus, it is possible toprevent the wound optical fiber from protruding above the optical fiberhousing means 44 due to bending or twisting. Therefore, it is possibleto more robustly house the optical fiber in the optical fiber housingmeans 44 and to prevent a situation in which the optical fiber isdetached from the guide.

Further, in the pluggable optical module 400, an opening 42 is disposedunder the projection 41. It is desirable that a width W1 of the opening42 is wider a width W2 of the projection 41. In this case, since theoptical fiber pressed by the projection 41 can be bent downward, housingof the optical fiber is facilitated. Further, even when a distancebetween a bottom surface of the optical fiber housing means 44 and alower surface of the projection 41 is short, it is possible to ensure aspace through which the optical fiber passes by disposing the opening42.

The optical fiber may also be configured to be derived downward from theoptical fiber housing means 44 through the opening 42, or to enter intothe optical fiber housing means 44 from the lower side of the opticalfiber housing means 44 through the opening 42 and to be wound around thecircular guide. According to this, it is possible to more easily performoptical wiring with respect to components placed under the optical fiberhousing means 44. Therefore, it is possible to increase a degree offreedom of arrangement of the optical fiber housing means 44 and othercomponents.

Other Exemplary Embodiments

The present invention is not limited to the above-described exemplaryembodiments, and can be modified as appropriate without departing fromthe scope of the invention. For example, in the exemplary embodimentsdescribed above, the configuration in which the optical output module 12and the optical reception module 13 are separately disposed and thelocal oscillation light LO is output from the optical output module 12to the optical reception module 13, it is not limited to thisconfiguration. For example, the optical output module 12 and the opticalreception module 13 may be configured as a single optical module and thelocal oscillation light may be exchanged between an output part and areception part of the optical module, for example, through the opticalfiber.

In the exemplary embodiments described above, the example in which thefirst to third optical fibers F11 to F13 are disposed. However, furtheroptical fiber may be disposed and housed in the optical fiber housingmeans as long as the further disposed optical fiber can be housed in theoptical fiber housing means. Note that it is not necessary to house allthe further optical fibers in the optical fiber housing means.

It is desirable that the optical fiber housing means is formed of amaterial having high thermal conductivity, for example. In this case,since it is possible to contribute to heat dissipation of othercomponents mounted in the vicinity of the optical fiber housing meansand the printed circuit board, it is possible to improve heat radiationperformance. Therefore, thermal runaway of a circuit can be suppressed.

The present invention has been described above with reference to theexemplary embodiments, but the present invention is not limited to theabove exemplary embodiments. The configuration and details of thepresent invention can be modified in various ways which can beunderstood by those skilled in the art within the scope of theinvention.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2015-120420, filed on Jun. 15, 2015, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   CON1 CONTROL SIGNAL-   DAT DATA SIGNAL-   F11 FIRST OPTICAL FIBER-   F12 SECOND OPTICAL FIBER-   F13 THIRD OPTICAL FIBER-   G11 TO G13, G21, G22, G31, G32 CIRCULAR GUIDES-   G33, G34 GUIDES-   LO LOCAL OSCILLATION LIGHT-   LS1, LS2 OPTICAL SIGNALS-   LORIG OUTPUT LIGHT-   MOD MODULATION SIGNAL-   PMA, PMB PHASE MODULATION AREAS-   SIG_M1, SIG_M2 MODULATION SIGNALS-   VBIAS BIAS VOLTAGE-   10 HOUSING-   11 PLUGGABLE ELECTRIC CONNECTOR-   12 OPTICAL OUTPUT MODULE-   13 OPTICAL RECEPTION MODULE-   14, 24, 34, 44 OPTICAL FIBER HOUSING MEANS-   14A, 24A, 44A PLATES-   15 PLUGGABLE OPTICAL RECEPTOR-   16 LIGHT SOURCE-   17 OPTICAL MODULATION UNIT-   17A OPTICAL MODULATOR-   17B DRIVER CIRCUIT-   30 SPLICE HOUSING-   31 SPLICE-   40 OUTER FRAME-   41 PROJECTION-   42 OPENING-   51 TO 54 PRINTED CIRCUIT BOARDS-   91, 92 OPTICAL FIBERS-   93 OPTICAL COMMUNICATION APPARATUS-   100, 200, 300, 400 PLUGGABLE OPTICAL MODULES-   171 TO 174 OPTICAL WAVEGUIDES-   1000 OPTICAL COMMUNICATION SYSTEM

The invention claimed is:
 1. A pluggable optical module comprising: a plurality of optical components including a pluggable electric connector being capable of connecting with an optical communication apparatus, a pluggable optical receptor being capable of connecting with outer optical fibers, an optical output module outputting a first optical signal and a local oscillation light, and an optical reception module receiving a second optical signal interfering with the local oscillation light; a printed circuit board with which the optical reception module is connected; a first optical fiber connecting between the optical output module and the pluggable optical receptor; a second optical fiber connecting between the optical output module and the optical reception module; a third optical fiber connecting between the optical reception module and the pluggable optical receptor; and an optical fiber housing unit comprising a guide configured to wind the first to third optical fibers, the optical fiber housing unit being mounted to be stacked with the printed circuit board and the optical output module.
 2. The pluggable optical module according to claim 1, wherein the optical fiber housing unit is mounted to interpose between a first printed circuit board and a second printed circuit board.
 3. The pluggable optical module according to claim 1, wherein the pluggable electric connector is configured to communicate a modulation signal, a communication data signal, and a control signal with the optical communication apparatus, the optical output module outputs the first optical signal modulated in response to the modulation signal, the optical reception module outputs the communication data signal converted from the received second optical signal, the outer optical fibers comprise a transmission optical fiber and a reception optical fiber, the pluggable optical receptor is configured to output the first optical signal to the transmission optical fiber and can forward the second optical signal from the reception optical fiber to the optical reception module, the first optical signal propagates through the first optical fiber, the local oscillation light propagates through the second optical fiber, the second optical signal propagates through the third optical fiber, and extra lengths of the first to third optical fibers are wound and housed by the guides.
 4. The pluggable optical module according to claim 3, wherein both of the optical output module and the optical reception module are mounted on the printed circuit board.
 5. The pluggable optical module according to claim 4, wherein the optical fiber housing unit is mounted in such a manner that a surface of the optical fiber housing unit on which the first to third optical fibers are housed faces a side opposite to a part or all of the optical output module, the optical reception module, and the printed circuit board that are stacked.
 6. The pluggable optical module according to claim 4, wherein the optical fiber housing unit comprises: a plate; and at least two guides formed on the plate, and each of the first to third optical fibers is wound and housed in any of a first path circling one of the two guides, a second path circling to surround the two guides, and a third path circling each of the two guides, in a combination of two of the first to third paths, or in a combination of three of the first to third paths.
 7. The pluggable optical module according to claim 6, wherein a part or all of the first to third optical fibers include a splice, and the optical fiber housing unit further comprises a splice housing that is formed on the plate and configured to house and fix the splice.
 8. The pluggable optical module according to claim 6, wherein the optical fiber housing unit comprises first to third guides formed on the plate and configured to respectively wind and house the first to third optical fibers.
 9. The pluggable optical module according to claim 6, wherein the optical fiber housing unit comprises fourth to seventh guides, and each of the first to third optical fibers is wound and housed by using a path that is a combination of a part or all of the fourth to seventh guides.
 10. The pluggable optical module according to claim 6, wherein the guide includes a projection that projects outward from an outer perimeter of the guide, and the first to third optical fibers pass under the projection of the guide.
 11. The pluggable optical module according to claim 10, wherein the optical fiber housing unit further comprises an opening that is disposed under the projection of the guide, penetrates the plate, and has a width larger than the projection of the guide.
 12. The pluggable optical module according to claim 6, wherein the optical fiber housing unit further comprises an outer frame that is disposed on the plate and formed to surround the guide, the outer frame includes a projection that projects to the guides, and the first to third optical fibers pass under the projection of the outer frame.
 13. The pluggable optical module according to claim 12, wherein the optical fiber housing unit further comprises an opening that is disposed under the projection of the outer frame, penetrates the plate, and has a width larger than the projection of the outer frame.
 14. A pluggable optical communication system comprising: a first optical fiber configured to transmit an optical signal; a pluggable optical module configured in such a manner that the first optical fiber is insertable into and removable from the pluggable optical module, the pluggable optical module outputting the optical signal to the first optical fiber; and an optical communication apparatus configured in such a manner that the pluggable optical module is insertable into and removable from the optical communication apparatus, wherein the pluggable optical module comprises: a plurality of optical components including a pluggable electric connector being capable of connecting with the optical communication apparatus, a pluggable optical receptor being capable of connecting with outer optical fibers, an optical output module outputting a first optical signal and a local oscillation light, and an optical reception module receiving a second optical signal interfering with the local oscillation light; a printed circuit board with which the optical output module is connected; the first optical fiber connecting between the optical output module and the pluggable optical receptor; a second optical fiber connecting between the optical output module and the optical reception module; a third optical fiber connecting between the optical reception module and the pluggable optical receptor; and an optical fiber housing unit comprising a guide and configured to wind the first to third optical fibers, the optical fiber housing unit being mounted to be stacked with the printed circuit board and the optical output module.
 15. The optical communication system according to claim 14, wherein the optical fiber housing unit is mounted to interpose between a first printed circuit board and a second printed circuit board.
 16. The optical communication system according to claim 14, wherein: the pluggable optical module comprising: the pluggable electric connector is configured to communicate a modulation signal, a communication data signal, and a control signal with the optical communication apparatus, the optical output module outputs the first optical signal modulated in response to the modulation signal, the optical reception module outputs the communication data signal converted from the received second optical signal, the outer optical fibers comprise a transmission optical fiber and a reception optical fiber, the pluggable optical receptor is configured to output the first optical signal to the transmission optical fiber and forward the second optical signal from the reception optical fiber to the optical reception module, the first optical signal propagates through the first optical fiber, the local oscillation light propagates through the second optical fiber, the second optical signal propagates through the third optical fiber, extra lengths of the first to third optical fibers are wound and housed by the guides.
 17. The optical communication system according to claim 16, wherein both of optical output module and the optical reception module are mounted on the printed circuit board.
 18. The optical communication system according to claim 17, wherein the optical fiber housing unit is mounted in such a manner that a surface of the optical fiber housing unit on which the first to third optical fibers are housed faces a side opposite to a part or all of the optical output module, the optical reception module, and the printed circuit board that are stacked.
 19. The optical communication system according to claim 16, wherein the optical fiber housing unit comprises: a plate; and at least two guides formed on the plate, and each of the first to third optical fibers is wound and housed in any of a first path circling one of the two guides, a second path circling to surround the two guides, and a third path circling each of the two guides, in a combination of two of the first to third paths, or in a combination of three of the first to third paths.
 20. The optical communication system according to claim 19, wherein a part or all of the first to third optical fibers include a splice, and the optical fiber housing unit further comprises a splice housing that is formed on the plate and configured to house and fix the splice. 